(1) Field of the Invention
The invention relates to relief valves and more particularly to a two-way relief valve, positioned between first and second chambers having varying pressure therein, in order to relieve excess pressure in the first chamber and permit the pressurized medium to exit the first chamber and enter the second chamber, and vice-versa, through a common passageway.
(2) Description of the Prior Art
Pressure relief valves are used to substantially equalize pressure between a chamber and the atmosphere or between two chambers. Typically, the two chambers are adapted to contain dissimilar fluids, such as fuel and air. Such chambers may be disposed in a device for operating in an underwater environment calling for adjacent storage of fluids under pressure. In an underwater environment, the device and chambers may be subject to high underwater pressures as well as high differential pressures. Under such pressures, fluid in one chamber may cause distortion and rupture of the chamber and permit the fluid to enter an adjacent chamber or to escape from the device itself, causing failure of the device. Expected pressure fluctuations within each chamber may also require distinct pressure relief set points for each chamber.
A pair of one way relief valves can function to provide separate relief settings for each chamber, but space available in the device may not permit the use of two valves.
The prior art two-way relief valves are of two types. The first, as illustrated by U.S. Pat. No. 4,773,444, provides one pressure relief set point for the two chambers through a single biasing means common to both chambers. Such valves normally react to total dynamic pressure of the two chambers and are not suited to sensing the differential static pressure between chambers and cannot provide separate pressure relief set points.
The second type, as illustrated by U.S. Pat. No. 4,317,467, consists of a single seat valve utilizing a flexible diaphragm between the two chambers. The diaphragm has a central opening, the edges of which seal against a ball element. Excess pressure on the diaphragm side of the valve forces the diaphragm to flex and move with the ball element in a direction away from the excess pressure until the diaphragm encounters stops. The ball element continues to move, away from the diaphragm, allowing flow through the central opening in the diaphragm. Excess pressure on the ball side of the valve forces the diaphragm to flex in a direction away from the excess pressure. The ball element and diaphragm move together until the ball element encounters a stop. The diaphragm continues to flex away from the ball element allowing flow through the diaphragm opening. While this valve can provide separate pressure relief set points for each chamber and senses differential static pressure, the flexible diaphragm is not suited for use in high pressure applications. The high pressure differentials possible in an underwater environment can cause distortion of the flexible diaphragm leading to leakage between the chambers under normal working conditions. Also the single valve seat arrangement of such devices restricts flow through a single opening in the diaphragm. Under the anticipated high pressures in an underwater environment, such flow restriction can lead to rupture of the diaphragm or of the chamber and device containing the chamber.